This invention relates to an integrated circuit device, and more particularly to a hybrid integrated circuit device.
In the manufacture of the prior art hybrid integrated circuit devices, leads are connected to a lead connecting conductor layer formed on a ceramic substrate by inserting the T-shaped heads of the lead through small holes penetrating the conductor layer and substrate until the T-shaped heads reach the back side of the substrate. At this stage, various circuit elements such as IC elements, resistors, capacitors and the like have already been provided on the substrate. After the leads, as well as the circuit elements, have been set in the ceramic substrate, the substrate is put into a furnace to solder the circuit elements and leads to the substrate by reflow soldering. Thereafter, resistor layers, for instance, which are formed on the substrate, are trimmed to adjust their resistance to a predetermined value and wire-bonding is carried out for the IC elements. The trimming operation and the wire-bonding operation for the IC elements are very inconvenient since the leads project from the substrate. Also, the automation of the trimming and wire-bonding operations is very difficult because of the projecting leads. Further, in order to connect the leads to the substrate, they have to be inserted through the holes formed in the substrate from the back side thereof. Therefore, the operation of mounting leads has very poor control properties, and its automation is also very difficult.
To overcome the above drawbacks, it has been proposed to mount circuit elements other than leads on the substrate by reflow soldering, subsequently trim the resistors and the like and wire-bond the IC elements and then bond the individual leads to the substrate by means of soldering using infrared rays, a laser beam or a soldering iron. In this method, however, the substrate has to be washed once after the first reflow soldering process and before the trimming and once again after the leads have been bonded. Further, since two soldering processes are involved, the soldering portions are heated twice. Therefore, a phenomenon occurs wherein the solder is diffused into the lead connecting conductor layer formed on the substrate. This phenomenon deteriorates the mechanical strength of the soldered portions.
It has further been proposed to weld leads to the lead connecting conductor layer on the substrate by percussion welding. According to this method, however, splash is produced between the lead and lead connecting conductor layer to reduce the reliability of the hybrid integrated circuit device.